HUD Optical Path Correction for Ghosting and Image Rotation
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Solution Overview
Problem
HUD systems face challenges with image rotation and ghosting due to off-center placement, leading to increased complexity, cost, and alignment issues, and require additional components to compensate for these effects.
Innovation Solution
A single heads-up display unit incorporating a projector, splitting element, and freeform mirror to correct optical issues such as ghosting and image rotation, allowing for precise alignment and versatile use across different applications without additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a HUD unit is placed off center from the combiner to reduce size and accommodate other components, then the device complexity and cost are reduced, but the projected image appears rotated to the user
Solution Approach 1:
A freeform mirror is introduced as an intermediary optical element between the projector and combiner to correct image rotation. The freeform mirror compensates for the rotational distortion caused by off-center placement, allowing the HUD unit to maintain its compact configuration while delivering a properly oriented image to the user.
Solution Approach 2:
The patent employs a freeform mirror with specifically designed surface parameters to correct image rotation. By carefully controlling the mirror's geometric parameters and positioning, the system compensates for rotational distortion without requiring additional active adjustment mechanisms, thus maintaining device simplicity while improving image quality.
2Ease of operation
If a HUD unit is physically rotated to reduce image rotation effect, then the image orientation is improved, but alignment of other projection features becomes complex leading to lower resolution, brightness differences, and reduced contrast
Solution Approach 1:
The freeform mirror serves as a mediating optical element that corrects image orientation without requiring physical rotation of the entire HUD unit. This maintains precise alignment of projection features with the combiner while achieving the desired image orientation, thereby preserving resolution, brightness uniformity, and contrast.
Solution Approach 2:
The optical correction function is segmented from the main HUD unit structure. Instead of rotating the entire assembly, only the freeform mirror is designed with specific corrective properties, allowing independent optimization of image orientation while maintaining the precision alignment of other projection components.
3Ease of operation
If additional components are added to the HUD unit to compensate for rotation effects, then image orientation is improved, but the device complexity and cost increase
Solution Approach 1:
A single freeform mirror is introduced as an efficient intermediary element that provides comprehensive correction for image rotation. This solitary component replaces what would otherwise require multiple adjustment mechanisms or complex mechanical assemblies, thereby improving image orientation while minimizing the increase in device complexity.
Solution Approach 2:
The freeform mirror performs multiple functions simultaneously: it corrects image rotation, maintains proper alignment with the combiner, and preserves image quality parameters. This multi-functionality in a single component avoids the need for multiple separate correction devices, reducing overall system complexity.
4Object-affected harmful factors
If the combiner is manufactured with a wedged shape to reduce ghosting, then ghosting effects are reduced, but a specific windshield must be paired with a specific HUD unit increasing manufacturing burden and cost
Solution Approach 1:
The ghosting correction function is extracted from the combiner/windshield structure and relocated to the HUD unit itself. By incorporating a splitting element and freeform mirror within the HUD unit, the system corrects ghosting effects independently of the combiner's geometry, allowing any standard combiner shape to be used without requiring a wedged configuration.
Solution Approach 2:
The patent uses a splitting element that creates a virtual copy of the optical path to compensate for ghosting. By splitting and recombining light paths through the freeform mirror, the system effectively cancels out ghosting artifacts without modifying the combiner structure, thereby maintaining manufacturing flexibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a compact, cost-effective, and versatile HUD unit that corrects ghosting and image rotation, improving alignment and reducing the need for additional components and user adjustments.
Implementation Method 1
a splitting element within the housing and a freeform mirror within the housing. The splitting element is operable to split the projected image ray into at least two image rays
Implementation Method 2
The freeform mirror is operable to reflect the at least two image rays such that the optical path of the at least two image rays is corrected
Data Source
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AI summary
A heads-up display unit and a method of adjusting a projected image with the heads-up display unit comprising projecting, by a projector, an image comprising an image ray toward a combiner. The method further comprising splitting, by a splitting element, the image ray before the image ray hits the combiner. The method further comprising reflecting, by a freeform mirror, the image ray or the split image rays before the image hits the combiner. The method further comprising projecting the split and reflected image rays onto the combiner.